I have a 440, 26" champion 3 row with no shroud, 440 source aluminium water pump with matched pump/gasket and a 195 T-stat. No problems. In your case, the 22" rad may be the sole culprit. Or you could have a poor match with your water pump and housing. Some pumps will not work with some housings. The impeller depth in the housing in important. If it is off, you lose flow. Check to make sure you are using recommended pump/gasket/housing.
Toss the 160 stat. It will only cause your engine to wear out faster than it should. It won't help a cooling system that has a problem.
Buy a 195 stat, but put it in a pot of boiling water first and make sure it works as it should.
If you have those corrugated rad hoses, replace them. They cost flow.
If you have a hose(s) with a spring in it, replace it with one without a spring. They cost flow.
Perhaps buy a new rad cap. 16#. If the system can't pressurize, it will vent (steam off) earlier than it should.
That's all I can think of. Hope it helps.
PS. Depending on the cost of your IR gun, they can be very inaccurate. If you can, try to verify it's accuracy. Some read different temps depending on the surface colour/condition (in my experience anyway). Maybe aim it at a pot of boiling water and ensure it is close to 212*.